POS0463 ASSOCIATION OF CIRCULATING LEVELS OF ANTI-CARP ANTIBODIES WITH DISEASE ACTIVITY AND RADIOLOGICAL DAMAGE IN RHEUMATOID ARTHRITIS PATIENTS
Authors: M. Markovic, C. Campochiaro, B. Glisic, M. Petronijevic, G. Ristic, I. Stanojevic, D. Vojvodic, N. Viapiana, M. Matucci-Cerinic, L. Dagna
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> In rheumatoid arthritis (RA) the identification of specific autoantibodies is crucial for an earlier diagnosis and stratification of patients according to different disease phenotypes. Autoantibodies directed against carbamylated proteins (anti-CarP) have been recently identified [1] as predictors for RA development [2]. Anti-CarP antibodies are associated with more severe RA, in particular in anti-citrullinated peptide antibodies (ACPA) negative RA patients [3]. <h3>Objectives</h3> To determine the frequency of positive anti-CarP antibody in a real-life cohort of RA patients on synthetic and biologic disease-modifying antirheumatic drugs (DMARDs) and their association with radiological damage and disease activity. <h3>Methods</h3> The study is an open-label, observational, cross-sectional study, including 69 patients with RA according to ACR/ EULAR 2010 criteria, treated with synthetic and biological DMARDs. The control group consisted of 16 healthy controls (HC). The study was approved by institutional Ethical Committee and patients signed the Informed Consent. Circulating levels of anti-CarP antibodies were determined at baseline visit by commercial ELISA anti-CarP quantitative sandwich immunoassay (cut-off value 6 ng/ml). Articular X-rays were performed within 6 months of the baseline to define the presence of erosions. RA disease activity (DAS28 CRP) was assessed. Pearson χ<sup>2</sup> test, Wilcoxon test or Kruskall- Wallis test was used, as appropriate. Spearman rank-order correlation coefficient was applied for continuous variables. A multivariable logistic regression model was performed to assess prognostic variables on damage. <h3>Results</h3> Anti-CarP antibodies were positive in 35% of RA patients and no antibodies were found in HC. One quarter (4/17) of seronegative RA patients were anti-CarP positive. All anti-CarP positive and RF/ ACPA negative patients had radiological evidence of erosions and a moderate disease activity (DAS28 CRP 3.60± 0.58) and disability (HAQ-DI 0.70± 0.13). In all RA patients, a positive correlation between levels of anti-CarP antibodies and DAS28 CRP (p =0.0003; Spearman r = 0.4829) was found. Furthermore, 87% of anti-CarP positive patients had erosions. The multivariable logistic regression model suggested that disease activity and higher levels of anti-Carp antibodies were significant predictors for the presence of erosions. There was a greater number of erosions in patients with active disease (OR 1.31, 95% CI [1.14, 1.63]) and those with a higher levels of anti-CarP antibodies (OR1.66,95% CI [1.28, 2.37]). <h3>Conclusion</h3> Anti-CarP antibodies were present in a significant number of RA patients and those with higher circulating levels had higher disease activity and a greater occurrence of radiological damage. Further larger studies are warranted to better understand the clinical significance of anti-CarP antibodies in RA. <h3>References</h3> [1]Shi J, Knevel R et al. Autoantibodies recognizing carbamylated proteins are present in sera of patients with rheumatoid arthritis and predict joint damage. Proc Natl AcadSci U S A. 2011 Oct 18;108(42):17372-7. [2]Brink M, Verheul MK et al. Anti-carbamylated protein antibodies in the presymptomatic phase of rheumatoid arthritis, their relationship with multiple anticitrulline peptide antibodies and association with radiological damage. Arthritis Res Ther. 2015 Feb 7;17:25. [3]Yee A, Webb T et al. Anti-CarP antibodies as promising marker to measure joint damage and disease activity in patients with rheumatoid arthritis. Immunol Res. 2015 Feb;61(1-2):24-30. <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> None Declared.